The Kyoto Protocol

It commits the industrialized countries who've ratified it to reduce their emissions of six gases implicated in global warming by an average of at least 5 percent. That would take them back to 1990 levels. These goals are to be achieved by 2008-2012.

Signators have some flexibility in how they attain these emissions reductions. Developing countries don't have to cut back. Neither does the United States, which has not ratified the treaty.